Red light laser

ABSTRACT

A semiconductor material vertical cavity surface emitting laser for emitting narrow linewidth light comprising a compound semiconductor material substrate and pairs of semiconductor material layers in a first mirror structure on the substrate of a first conductivity type each differing from that other in at least one constituent concentration and each first mirror pair separated from that one remaining by a first mirror spacer layer with a graded constituent concentration. An active region on the first mirror structure has plural quantum well structures separated by at least one active region spacer layer and there is a second mirror structure on the active region similar to the first but of a second conductivity type. A pair of electrical interconnections is separated by said substrate, said first mirror structure, said active region and said second mirror structure.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Provisional Patent ApplicationNo. 60/780,267 filed Mar. 7, 2006 for “RED LIGHT LASER”.

BACKGROUND OF THE INVENTION

The present invention relates to Vertical Cavity Surface Emitting Laser(VCSEL) chips and subassemblies.

VCSELs are an important optical source for fiber optic datacommunication systems. Most of the devices that have been used in thesesystems emit light in the 830 to 860 nm wavelength range. However,VCSELs have been fabricated that have demonstrated emission atwavelengths equal to or in the vicinity of the following wavelengthvalues: 660 nm, 780 nm, 850 nm, 980 nm, 1310 nm, and 1550 nm.

Red light emission VCSELs (˜660 nm) are of considerable interest forapplications in which the emission light capable of being seen by thehuman eye is valued. For instance, photoelectric sensors attuned todetecting such emission light might be used to sense thepresence/absence, distance or other attribute of objects illuminated bythat light. The ability of an observer to see the emitted beam forsensor alignment purposes is advantageous. A bar code scanner would be aspecial case of such a sensor, and users prefer the use light thereby ofa visible wavelength so that they can more easily aim the light beam atthe bar code. Chemical, biological, or medical sensors can takeadvantage of the absorption or scattering of light having a particularemitted wavelength or wavelength range. An example of this would be apulse oximeter which relies on the relative absorption of 665 nm and 905nm wavelength light sources to determine the oxygen content of bloodbeing measured. Display or printing devices may rely on emitted light ofsuch shorter wavelengths to provide higher resolution.

The intended use or uses for systems with such red light emission VCSELsin them determines the attributes thereof that are of interest includingemitted light wavelength, power conversion efficiency, emissiondivergence angle and the emission mode structure. The mode structuredescribes the shape of the emitted beam. Some uses require a single modedevice, i.e. a device with a uniform round Guassian shaped lightemission intensity profile.

FIG. 1 is a fairly general schematic layer diagram of a typicalthin-film semiconductor material red light emitting VCSEL structureformed on a substrate, 1. The mirrors, 2 and 3, forming the opticalresonance cavity are constructed from AlGaAs materials having relativelylarge refractive index thin-film layers with a composition ofapproximately Al_(0.5)Gs_(0.5)As alternating with relatively smallrefractive index thin-film layers with a composition of Al_(x)Ga_(1-x)Aswhere the mole fraction x>0.85. Each such layer has a thicknesscorresponding to one quarter of an optical wavelength (λ/4) for thelight intended to be emitted by the VCSEL in the material of interestfor that layer. The optical thickness is defined by the wavelengthdivided by the refractive index. For instance, if the emissionwavelength is 670 nm, and the composition is GaInP which has arefractive index of 3.65. The optical thickness corresponding to onewavelength in the material would then be (670 nm)/3.65=183.6 nm. Withinthe mirror, the layers are one quarter wavelength thick, and so themirror layers would be in the range of 45 nm thick. Many periods (>20)of alternating quarter wavelength thick layers of these two materialsforms a highly reflective mirror at the intended emission wavelength.Mirror 2 is doped to be of n-type conductivity, and mirror 3 is doped tobe of p-type conductivity with a highly doped doping grading layer, 3′,thereon having a thickness of 2nλ/4 with n being an integer.

The active region, 4, of the VCSEL between mirrors 2 and 3 is formedfrom a AlGaInP materials system. One or more quantum wells are includedin the structure formed of corresponding thin-films with a compositionapproximately equal to Ga_(0.5)In_(0.5)P. The injected carriers arecaptured by these quantum wells and then combine to thereby emit light.The composition and thickness of each quantum well thin-film togetherdetermines the emission, or photoluminescence, wavelength of the quantumwells. The quantum wells are spaced apart by barrier thin-film layers ofAlGaInP, and together are bounded on either side in active region 4 bycladding, or confining, layers, 5 and 6, also of AlGaInP, with thecompositions both barrier and cladding layers being chosen such thatthey are lattice constant matched to GaAs which will serve as the devicesubstrate, and so that they have a bandgap that is larger than that ofGaInP for thereby providing photon confinement. The total thickness ofthe active region is typically one wavelength (1λ) of the light intendedto be emitted by the VCSEL thick although it can be any integer multipleof one half of the emission wavelength (nλ/2). A highly doped GaAscapping layer, 7, is provided on doping grading layer 3′ to togetherreduce electrical resistance in lateral directions.

One of the constraints for the overall VCSEL epitaxial structure is thatthe lattice constant or parameter of the layers in the structure benearly equal to that of the underlying GaAs substrate. If this is nottrue, then lattice defects can form which may cause damage to the deviceas the device is used and so limit the reliability or lifetime of thedevice. In the AlGaAs materials system, this condition is met for allpossible compositions trading off aluminum for gallium ranging from AlAsto GaAs. However, in the AlGaInP materials system, this condition is metonly for the compositions corresponding to(Al_(x)Ga_(1-x))_(y)In_(1-y)P, where the mole fraction y=0.51. The molefraction x can be adjusted from 0 to 1.0 without affecting the latticematch to GaAs. However, the bandgap discontinuities in AlGaInP can beadjusted somewhat by adding small amounts of strain to the quantum wellsand barrier layers by slightly adjusting the value of y and thethickness of the layers. If the total thickness of the strained layersis kept sufficiently thin (100-200 nm) then defects do not form, and thedevice reliability is not affected.

Confinement of electrical currents to desired locations in the structurecan be provided with the standard techniques of ion implantation andoxide aperture formation as shown in the more general schematic layerdiagram of FIG. 2 of the FIG. 1 VCSEL structure having the samesemiconductor material layers. There, such structures as an implant oroxide confining layer, 8, and a top metal interconnection, 9, with anemission aperture are indicated. Substrate 1 has another metalinterconnection, 1′, provided on the exposed outer surface thereof.Other useable alternatives exist for this purpose which have beendemonstrated in VCSELs emitting light at other wavelengths.

Red light emission VCSELs have been demonstrated, but, typically, thetemperature range of operation is limited and the maximum output power,particularly single mode output power, is also limited. These limitsbecome more significant for shorter wavelength devices. Due to the smallbandgap discontinuities and the low thermal conductivities inAlGaInP—AlGaAs material systems, the output power of red light emissionVCSELs decreases if the emission wavelength decreases or the operationtemperature increases, or both. Small bandgap discontinuities means thatcarriers that should be captured in the quantum wells and recombinedthere to emit light, instead, escape and so don't contribute to thelight output. As the temperature increases, the charge carriers are evenmore likely to escape those wells. For shorter wavelength devices, thequantum well needs to be shallower in order to generate the higherenergy, or shorter wavelength, light but this also contributes to theescape of charge carriers. Thus, there is a very significant increase indifficulty between achieving high performance in a device emitting at650 nm versus one emitting at 670 nm, for instance.

Another issue which plays a role in the temperature range of operationis the electrical resistance of the AlGaAs mirrors. TheAl_(0.5)Ga_(0.5)As composition, which constitutes approximately 50% ofthe mirror thickness, has poor thermal conductivity. In addition, themany periods in the mirror contributes to an increase in the resistance,which results in additional heating. The additional heating combinedwith the extra sensitivity of this material system to temperature onlyexacerbates the problem. These factors combine to make providing a redlight emission VCSEL device with substantial single mode output powerparticularly difficult. Further, the smaller aperture size of the singlemode device typically means that these devices heat more quickly. Thus,there is a desire to have a red light emission VCSEL device configuredto be less bounded by such limitations.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a semiconductor material vertical cavitysurface emitting laser for emitting narrow linewidth light comprising acompound semiconductor material substrate and at least two first mirrorpairs of semiconductor material layers in a first mirror structure onthe substrate of a first conductivity type each differing from thatother in at least one constituent concentration and each first mirrorpair separated from that one remaining by a first mirror spacer layerwith a graded constituent concentration. An active region on the firstmirror structure has plural quantum well structures separated by atleast one active region spacer layer and at least two second mirrorpairs of semiconductor material layers in a second mirror structure onthe active region of a second conductivity type each differing from thatother in at least one constituent concentration and each pair separatedfrom that one remaining by a second mirror spacer layer with a gradedconstituent concentration. A pair of electrical interconnections isseparated by said substrate, said first mirror structure, said activeregion and said second mirror structure. The quantum well structures canbe under stress in one direction with the active region spacer layerunder stress in an opposite direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a general schematic layer diagram for an epitaxial layerstructure for a red light emission VCSEL,

FIG. 2 shows a more general schematic layer diagram of a red lightemission VCSEL structure adding electrical operation structures,

FIG. 3 shows a table setting out an epitaxial layer structure of a redlight emission VCSEL embodying the present invention,

FIG. 4 shows a portions of schematic layer diagrams embodying part ofthe present invention,

FIG. 5 shows a portion of schematic layer diagram embodying a part ofthe present invention,

FIG. 6 shows another table setting out an epitaxial layer structure ofan alternative red light emission VCSEL of the present invention,

FIG. 7 shows a portions of schematic layer diagrams embodying part ofthe present invention,

FIG. 8 shows a portion of schematic layer diagram embodying a part ofthe present invention,

FIG. 9 shows a schematic layer diagram of an alternative red lightemission VCSEL embodying the present invention with electrical operationstructures,

FIG. 10 shows a top view of the red light emission VCSEL device shown inFIG. 9,

FIG. 11 shows a schematic layer diagram of an alternative red lightemission VCSEL embodying the present invention with electrical operationstructures,

FIG. 12 shows a schematic layer diagram of an alternative red lightemission VCSEL embodying the present invention with electrical operationstructures,

FIG. 13 shows a schematic layer diagram of an alternative red lightemission VCSEL embodying the present invention with electrical operationstructures,

FIG. 14 shows a schematic layer diagram of an alternative red lightemission VCSEL embodying the present invention,

FIG. 15 shows a layout of a monolithic integrated circuit chip with anarray of the red light emission VCSEL devices of the present invention,

FIG. 16 shows a housing arrangement for an array of the red lightemission VCSEL devices of the present invention,

FIG. 17 shows a housing arrangement for an array of the red lightemission VCSEL devices of the present invention, and

FIG. 18 shows a housing arrangement for a red light emission VCSELdevice of the present invention.

DETAILED DESCRIPTION

FIG. 3 is a tabular layer listing for a red light emitting VCSEL deviceindicating the thin-film semiconductor material epitaxial layers forthat red VCSEL device, a device that relieves the foregoing limitations.Each of the 33 layers in the table for the VCSEL device structure isspecified with respect to its composition, thickness, dopant type anddopant concentration.

The epitaxial structure is grown on a GaAs semiconductor materialsubstrate that is doped n-type, and is labeled layer number 0 in thetable. The substrate major surface on which the further layers are to bedeposited should be misoriented from the (100) orientation by 6 to 10°.This choice provides an improvement in the optical quality of theAlGaInP layers of the active region where the emitted light isgenerated. However, a higher degree of misorientation results in atendency for the high aluminum containing layers of the mirror tooxidize or otherwise degrade at an accelerated rate.

Device mirrors, 2′(layers 2 through 10) and 3′(layers 21 through 32),are made up of two kinds of primary layers alternating with each in adevice layer stack with each comprised of one of two differingcompositions of Al_(x)Ga1 _(1-x)As, that is, an AlAs layer free ofgallium alternating with an Al_(0.5)Ga_(0.5)As layer. These primarylayers are spaced apart with layers in between in which the aluminum andgallium distributions are mole fraction graded monotonically over thelayer thickness to match the gallium content in the primary layers oneither side of the graded spacer layers. While it is desirable for thegallium content of the two primary layers to differ as much as possiblein order to maximize the reflectivity to the light intended to beemitted, the minimum aluminum composition is limited to around a molefraction value x=0.5 in order to eliminate absorption due to the bandedge.

Mirror 2′ closest to the substrate is doped to be of n-type conductivitywith silicon. Numerous other n-type dopants could alternatively be used,including tellurium and selenium. Mirror 3′ on the opposite side of adevice active region, 4′, has the same range of compositions and withsimilar monotonically graded spacer layers between the two primarylayers, but is doped to be of p-type conductivity with carbon. Otherp-type dopants could alternatively be used, such as zinc or magnesium.The total thickness of a mirror layers repeatability period is ½λ whereλ is the desired wavelength within the range of 650 nm to 680 nm.

The details of the layer thicknesses and doping concentrations arechosen to minimize the electrical resistance of the device withouthaving an unduly negative impact on the optical reflectivity of themirror or on optical absorption. The thickness of the graded spacerlayers is shown to be around 20 nm. The thicknesses of the other twolayers are each approximately equal to the ¼λ minus the thickness of agraded spacer layer. The thickness of the graded spacer layer should beat least 10 nm thick to reduce the electrical resistance of the mirrorwithout reducing the optical reflectivity thereof An optimum thicknessis typically in the range of 20 to 25 nm.

The choice of doping concentration is also a matter of balancing thedesire to reduce resistivity by increasing the doping concentration,without increasing the optical absorption due to free carrierabsorption. In the six periods of n-type conductivity mirror 2′ closestto active region 4′, the doping is 5·10¹⁷/cm³ in the Al_(0.5)Ga_(0.5)Aslayers and AlAs layers, and is graded over the layer thickness from1·10¹⁸/cm³, at the side of the graded spacer layers closest to theadjacent AlAs layer, to 5·10¹⁷/cm³ at the side of the graded spacerlayers closest to the adjacent Al_(0.5)Ga_(0.5)As layers. In theremainder of the n-type conductivity mirror, the doping is uniform at alevel of 2·10¹⁸/cm³.

Within p-type conductivity mirror 3′, in the first six periods closestto the active region, the doping in the Al_(0.5)Ga_(0.5)As layers is5·10¹⁷/cm³, the doping in the AlAs layer is 1·10¹⁸/cm³, and is gradedover the layer thickness from 5·10¹⁷/cm³, at the side of the gradedspacer layers closest to the adjacent Al_(0.5)Ga_(0.5)As layer, to1·10¹⁸/cm³ at the side of the graded spacer layers closest to theadjacent AlAs layers. Inmost of the remainder of the p-type conductivitymirror, the doping is 1·10¹⁸/cm³ in the Al_(0.5)Ga_(0.5)As layers,2·10¹⁸/cm³ in the AlAs layers, and grades over the layer thickness from1·10¹⁸/cm³, at the side of the graded spacer layers closest to theadjacent Al_(0.5)Ga_(0.5)As layer, to 2·10¹⁸/cm³ at the side of thegraded spacer layers closest to the adjacent AlAs layers.

The lower doping in the mirror periods closest to the active region inboth p-type conductivity mirror 3′ and n-type conductivity mirror 2′ ischosen to reduce the free carrier absorption in the layers where theoptical field is highest. The more distant mirror periods have a weakereffect on absorption of the optical beam, and hence a higher dopingconcentration can be tolerated to aid in reducing the electricalresistance.

At the outer surface of p-type conductivity mirror 3′ in the device(outer surface of layer 30) there is provided a first Al_(0.5)Ga_(0.5)Aslayer, in which the doping is graded from 2·10¹⁸/cm³ to 3·10¹⁹/cm³, tothereby grade to the doping of a further layer of Al_(0.5)Ga_(0.5)Asthat is provided thereon doped to 3·10¹⁹/cm³. The outermost layer isGaAs and is doped at >1·10¹⁹/cm³. These three layers together come to athickness of approximately 9λ/4 thick where λ is the desired emissionwavelength of the device. The purpose of doping these topmost layers ofthe structure at a very high concentration is to provide a very lowlateral resistance in order to spread the device operating electricalcurrent evenly across the aperture of the device.

In the case where an oxide aperture is used for current confinement, thecompositions of the mirror are to be adjusted. Since the layer to beoxidized must contain a higher Al concentration than the other mirrorlayers, AlAs can no longer be used for the low index layer. TypicallyAl_(x)Ga_(1-x)As with x in the range from 0.85 to 0.95 would be used.However, if the oxide aperture is located in mirror 3′ between theactive layer and the metal interconnection with an aperture, then it ispreferable to continue to use AlAs as the low index layer in the othermirror (mirror 2′ closest to the substrate), in order to minimize theelectrical resistivity and maximize the thermal conductivity of thislatter mirror. On the other hand, 2 to 4 of the bottom mirror periodsclosest to the quantum well active region may also have a reducedaluminum content, in order to avoid accidental oxidization of theselayers when the aperture is being oxidized.

Other doping concentrations are possible for use ranging from a low of1·10¹⁷/cm³ in the six layer repeatability periods of mirrors 2′ and 3′closest to the active region to a high of 3·10¹⁸/cm³ in the remainingportions of those mirrors. However, concentrations within approximately±30% of the ones specified in FIG. 3 are typically optimum.

Other variations on mirror configurations can have benefits in reducingthe electrical resistance of the device or improving the thermalconductivity, or both, one of which is shown in the example of FIG. 4.FIG. 4A shows the schematic representation of mirror 2′ as configured inthe table of FIG. 3 above, i.e. having a quarter wave thickness of AlAs,or the low index layer of the mirror, that is alternated with a quarterwave thick layer of AlGaAs, or the high index layer of the mirror. Thealternative mirror, 2″, is shown in FIG. 4B. While the total thicknessof the mirror period remains at a half wavelength, the thickness of theAlAs layer is increased, while the thickness of the AlGaAs layer isdecreased. Since the AlAs layer has both a higher mobility, and a higherthermal conductivity, the resistance of the mirror is reduced, and thethermal conductivity is increased. The optical thickness of the AlAslayers is 50% greater than the optical thickness of theAl_(0.5)Ga_(0.5)As layers but any ratio greater than 1:1 will have apositive effect.

Yet another variation for reducing the electrical resistance of themirror structure is illustrated in FIG. 5. Since the mobility of n-typeconductivity AlAs and AlGaAs is significantly higher than that of p-typematerial, the electrical resistivity of the device in the table of FIG.3 above can be reduced by doping not only mirror 2′ thereof to be ofn-type conductivity but also doping mirror 3′ thereof to be of n-typeconductivity. Nevertheless, a pn junction is required for properfunctioning of the device. This can be accomplished by incorporating atunnel junction, 20, in an extended active region, 4 j′, of the deviceadjacent to that resulting n-type conductivity mirror, 3″, between thetunnel junction extending active region 4′ and capping layer 7. When thepn junction at quantum well active region 4′ is forward biased, tunneljunction 20 will be reverse biased. By highly doping the layers formingtunnel junction 20, the breakdown voltage can be made very low, so thatthis junction does not add much to the required drive voltage of thedevice. The highly doped layers (10¹⁹/cm³) are kept very thin, andlocated at an optical null in order to minimize their excesscontribution to the free carrier absorption loss. The tunnel junctioncomprises, sequentially grown, a highly doped n⁺⁺-conductivity typelayer, 21, followed by a p⁺⁺-conductivity type layer, 22, each having athickness of around 100 to 350 Å. The n-type conductivity layers have adoping concentration of approximately 2·10¹⁹/cm³ and the p-typeconductivity layers have a doping concentration of approximately8·10¹⁹/cm³.

In between the two mirrors 2′ or 2″ and 3′ or 3″ of the device of thetable in FIG. 3 or the mirror variations in FIGS. 4 and 5 are the layers(11 through 20) of active region 4′ as bounded on either side thereof bya corresponding one of a pair of cladding layers, 5′(layers 11 and 12)and 6′(layer 20), the region in which the injected charge carrierscombine with one another and emit light. These layers are based upon the(Al_(x)Ga_(1-x))_(y)In_(1-y)P material, which is lattice constantmatched to GaAs at a value of approximately mole fraction y=0.51.Hereafter, y will be specified only when it differs from a value of0.51.

Active region 4′ begins from mirror 2′ with a 60 nm thick ungradedspacer or cladding layer 5′ of Al_(0.7)Ga_(0.3)InP, doped to have an-type conductivity at a level of 5·10¹⁷/cm³, followed by a 15 nm thicklayer of the same composition but undoped. The next layer is a 20 nmthick layer of undoped Al_(0.4)Ga_(0.6)InP. The light generating layersconsist of the three Ga_(0.46)In_(0.54)P quantum wells of approximately7 nm thickness each seperated by two Al_(0.4)Ga_(0.6)InP barrier layerswith a thickness of 6 nm each, all undoped. This is followed by another20 nm thick layer of an undoped Al_(0.4)Ga_(0.6)InP composition. Activeregion 4′ is then ended on the side thereof opposite from where itbegins by Al_(0.7)Ga_(0.3)InP ungraded spacer or cladding layer 6′ witha thickness of 75 nm and doped p-type to a level of 1·10¹⁸/cm³ that islocated next to the structure of p-type conductivity mirror 3′. Thetotal thickness of the AlGaInP layers is adjusted to be equivalent tothe optical thickness of 1λ, where λ is again the desired emissionwavelength of the VCSEL. The thicknesses of the Ga_(0.46)In_(0.54)Pquantum well layers in active region 4′ are adjusted slightly to achievethe desired emission wavelength in the range of 640 to 670 nm dependingupon the desired emission wavelength within that range.

Active region 4′ of AlGaInP materials is chosen to provide the bestcarrier injection and carrier confinement in order to improve thewavelength and temperature range of operation, and to improve the outputpower. The quantum well composition of Ga_(0.46)In_(0.54)P is chosen toprovide a compressive strain of approximately 0.5%. This increases thewell depth, and increases the bandgap discontinuity between the quantumwells and surrounding barrier layers, to reduce carrier leakage. Thecomposition of the spacer, or cladding, layers 5′ and 6′ is also chosento be near the maximum band edge offset to provide improved carrierconfinement. Finally, the doping concentrations and locations are chosento provide a balance between good carrier injection, without undue freecarrier absorption. In particular, the use of a higher concentration ofp-doping with zinc (1·10¹⁸/cm³) provides an improved barrier to electronleakage into p-type conductivity mirror 3′ which would cause increasedoptical absorption.

The wavelength at the peak of the photoluminescence emission from thequantum wells is chosen to be 5 nm to 15 nm shorter than the Fabry-Perotresonance cavity mirror separation, or cavity emission wavelength, toenhance the higher temperature performance of the devices. Thisincreases the temperature range of operation since the peak of thequantum well emission moves to higher wavelengths with increasingtemperature faster than the Fabry-Perot resonance wavelength, theemission wavelength of the VCSEL cavity increases with temperature. Thismeans that the two are aligned at a temperature above room temperatureand so improves the higher temperature performance. The offset betweenthe cavity emission and the quantum well emission can be increased toachieve improved higher temperature performance, but this comes at thecost of an increased threshold current, and reduced output power at roomtemperature and below. The two considerations are balanced dependingupon the performance requirements of a particular use selected for thedevice.

FIG. 6 provides a tabular layer listing for a red light emitting VCSELdevice indicating the thin-film semiconductor material epitaxial layersfor an alternative red VCSEL device having a semiconductor materialthin-film epitaxial layer structure with 34 layers that allows thedevice to achieve a better performance at higher temperatures. Thelayers of mirrors 2′(layers 2 through 10) and 3′(layers 22 through 31)of this device are identical to those of the layer structure set out inFIG. 3 but an active region, 4″, therefor (layers 11 a through 21 b) hasAlGaInP layers that differ from those in the device of Table 3 asdescribed below.

Active region 4″ between mirrors 2′ and 3′ is still a total of 1λ thick,where λ is the desired optical emission wavelength. With the exceptionof the quantum wells and barrier layers, the In composition of all thelayers is chosen to be lattice constant matched to GaAs, i.e.approximately (Al_(x)Ga_(1-x))_(0.51)In_(0.49)P.

The first layer adjacent to n-type conductivity AlGaAs material basedmirror 2′ is a (Al_(0.7)Ga_(0.3))InP spacer, or part of a claddinglayer, 5″, (layers 11 a through 12) doped to have an n-type conductivityat 5·10¹⁷/cm³. Then, over a thickness of approximately 55 nm there isprovided a graded spacer layer, with the composition mole fractiongraded from x=0.7 to x=0.5. This layer is also doped to have n-typeconductivity at 5·10¹⁷/cm³. This is followed by an undopedAl_(0.5)Ga_(0.5)InP that is 14 nm thick.

Next are four barrier layers interleaved with three quantum well layers,all undoped. The quantum well layers are compressively strained with acomposition of Ga_(0.46)In_(0.54)P. Unlike the structure of FIG. 3, herethe barrier layers are arranged to be under tensile stress in order tocompensate the compressive stress of the quantum well layers. Theselayers are (Al_(0.5)Ga_(0.5))InP with the value of y adjusted to begreater than 0.51 to thereby provide a tensile stress of approximately0.35% in these layers.

After the fourth tensile stressed barrier layer is a cladding layer, 6″,beginning with lattice constant matched undoped Al_(0.5)Ga_(0.5)InPlayer with a thickness of 14 nm. A graded spacer then follows with itscomposition mole fraction graded from x=0.5 to x=0.7 over a thickness of55 nm. This layer is doped 1·10¹⁸/cm³. The final Al_(0.7)Ga_(0.3)InPspacer in cladding layer 6″ is 20 nm thick and doped 1·10¹⁸/cm³.

Thus, active region 4″ in this VCSEL has a balancing of the compressivestress of the quantum wells with the tensile stress of the interleavedbarrier layers to provide even better carrier confinement. The tensilestress, in combination with the compressively strained quantum wells,provides an even greater improvement in the quantum well depth than isobserved in a structure with lattice matched barrier layers andcompressively strained quantum wells of the same composition. Inaddition, the balancing of the strain makes it possible to decrease yeven more to create an even greater degree of compressive strain in thequantum wells without risking the generation of defects that would havea negative impact on device lifetime. In addition, the mole fractiongraded x=0.5 to x=0.7 AlGaInP layers also provide better carrierconfinement.

Another variation of the active region configuration is shown in theactive region representation diagrams of FIG. 7. FIG. 7A shows thearrangement of FIG. 6 with the use of Al_(0.7)Ga_(0.3)InP claddinglayers both for n-type conductivity cladding layer 5″ and for p-typeconductivity cladding layer 6″ in active region 4″. The variationinvolves the replacement of these Al_(0.7)Ga_(0.3)InP cladding layerswith AlAs layers of the same optical thickness (or an optical thicknessthat maintains the total cavity thickness at an integer multiple of λ/2)as shown in FIG. 7B. Thus, a n-type conductivity AlAs layer, 5′″, inFIG. 7B replaces layer 5″ of FIG. 7A and a n-type conductivity AlAslayer, 6′″, in FIG. 7B replaces layer 6″ of FIG. 7A to form an activeregion, 4′″. The AlAs layers still provide carrier confinement, but havea higher thermal conductivity, thus assisting in removal of heat.Thicker layers will be more effective in thermal management, but makecontrol of the thickness of the cavity more challenging.

FIG. 8 shows yet another variation at the active region. In this case athin GaP transition layer, 23, is included at the interface betweenn-type conductivity AlGaInP cladding layer 5″ and the first AlAs layersin mirror 2′ and a thin GaP transition layer, 24, is included at theinterface between the p-type conductivity AlGaInP cladding layer and thefirst AlAs layers in mirror 3′. A band discontinuity exists at theinterface between the AlAs and the AlGaInP, contributing to the voltagedrop across the device. The incorporation of a GaP transition layer thatis very thin (<10 nm) provides an intermediate step in the band energy,thus reducing the discontinuity. However, the GaP transition layers arenot lattice matched to the GaAs substrate, and so the thickness of theselayers must be kept very thin to avoid generating defects that mightdegrade the lifetime of the device.

In addition to the foregoing epitaxial layers, other structuralarrangements are provided in the devices to obtain current confinementand allow electrical contact so as to also improve the performance ofthe devices. FIGS. 9 and 10 show in a representative device schematicdiagram in a partial layer diagram and atop view of a device,respectively, which illustrate such features. Thus, there is shown a redlight VCSEL, 10, having a substrate, 11, with a metal interconnection,11′, provided on the exposed outer surface thereof. A n-typeconductivity material mirror, 12, is supported on substrate 11 and hasbetween it and a p-type conductivity mirror, 13, an active region, 14,both supported thereon. Mirror 13 has a capping layer, 17, supportedthereon with an oxide or implant confining layer, 18, therein, and ametal interconnection, 19, on the side of device 10 opposite that withinterconnection 11′ with interconnection 19 having therein an emissionaperture and being supported on that layer 17.

In FIG. 9, carrier confinement is obtained by providing a gain guidethrough an ion implantation to form confining layer 18 using protons.Protons are a material species which can penetrate through the ratherthick layers of the p-type conductivity mirror and make the materialwhere they come to reside insulating. The protons are implanted with anenergy that places the peak of the implantation for layer 18 at adistance of 2 to 6 mirror layer repeatability periods above activeregion 14 of VCSEL device 10. This carrier confinement structure couldalternatively be provided by an oxide aperture through growing a lowindex mirror layer in the structure with a Al composition thereingreater (>0.95) than the composition of the other low index mirrorlayers (which equals Al0.85), and then using a steam atmosphere at ahigh temperature to oxidize the high Al containing layer to form aninsulating Al₂O₃.

However, the implanted structure for layer 18 has several advantages. Itallows the use of AlAs in the top mirror which has a higher thermalconductivity than AlGaAs and thus will allow easier heat removal. Itgenerates less stress than does an oxide layer, and hence can result ina more reliable device. It provides a smaller contrast in refractiveindex, and hence can allow a single mode device to be made at a higherdiameter (up to 10 μm) than would be possible with an oxide aperture.

The correct aperture size for the aperture in layer 18 in a single modedevice with the gain guide provided by an ion implantation is 6μm<aperture diameter<μm, with 8 to 10 μm typically the optimum size. Asmaller diameter device would be required to achieve a single modedevice with an oxide aperture for carrier confinement.

The emission aperture in metal interconnection 19, which allows thelight to escape the device for emission, should nominally be the samediameter as the implant aperture ±0.5 μm though shown as of differentdiameters in FIG. 10. Equal metal and implant aperture diameterstypically provide the best combination of output power efficiency andlow lateral resistance (i.e. the current does not need to travel alonger lateral distance to reach the aperture.)

FIGS. 9 and 10 also show a device electrical isolation implantstructure, 25, to isolate one VCSEL device from its neighboring devicesin a multiple device monolithic integrated circuit chip so the injectedcarriers pass through the intended device rather than traveling to aneighboring device. This implantation is also more likely to beimplanted using protons, although it is conceivable that anotherspecies, such as oxygen, for instance, could be used if a highimplantation energy is available. The inner isolation implant diameteris large enough that it does not interfere with the metal contact to thedevice, i.e. with an inner diameter aperture which is at least 10 μmlarger than the inner diameter of the metal. The outer isolationdiameter should be 5 to 40 μm larger than the inner diameter. While itcould be “infinite” (a blanket implant everywhere except for thedevices) the narrower ring of an implant is expected to provide athermal advantage, i.e. unimplanted material is a better thermalconductor than the implanted material. The choice of the width of theimplanted ring is a balance between the need to provide good isolationbetween devices, with the desire to maximize the thermal conductivity.

A particular issue in red VCSEL devices is thermal lensing, i.e. theindex of refraction is affected by heating in a nonuniform manner. Boththe proton implant and the oxide aperture methods for providingelectrical and optical energy confinement in VCSELs present limitations.Generally, oxide apertures provide too strong index guiding resulting inmulti-mode devices for all but the smallest apertures. While single modedevices can be achieved for small aperture devices, the amount of singlemode output power achievable is limited by heating and current density.On the other hand, the weak index guiding provided by the proton implantcan allow single mode performance to be achieved at larger diameters,but thermal lensing becomes a problem, with the modal structure varyingas a function of temperature. When the device is to be modulated with avery wide bandwidth, the occurrence of thermal lensing can lead todifficulties in achieving modulation with a predictable and stableoutput power as a function of temperature.

One alternative red light VCSEL device, 10′, for maximizing the abilityto achieve high single mode output power while minimizing the thermallensing is to use a double proton implant, or a graded ion implantationtherein as is shown in the representative schematic diagram of FIG. 11.The lower energy implant layer, 18′, is shallower, and a mask forming asmaller diameter unimplanted region is used. The second, higher energyimplant, to form implant layer 18 is used with a mask that provides alarger diameter unimplanted region. The higher, smaller diameter implantlayer 18′ helps to guide the current flow to the center of the lowerimplant aperture, thus helping to counteract the thermal lensing effectthat guides current away from the center. However, this approach keepsthe current density in the active region consistent with a largerdiameter device which is important for achieving a larger single modeoutput power, and improve device lifetime.

This effect can also be refined by using multiple (>2) implant energiesand mask diameters, or possibly by the use of implantation done at anangle to achieve the effect of a smaller diameter implant toward thesurface of the device, and a larger diameter implant closer to theactive region.

Yet another alternative, 10″, for achieving mode control and a largerdiameter single mode in a red light. VCSEL device is shown in therepresentative schematic diagram of FIG. 12. This uses a combination ofan ion implantation aperture and an oxide aperture. The specificimplantation is to provide proton implant layer 18 to a depth centeredclose to quantum well active region 14, i.e. centered anywhere from thequantum well active region to four periods above the quantum wells. Inaddition, an oxide layer, 18″, with an aperture is formed at a positiongreater than six periods toward interconnection 19 from quantum wellactive region 14 in order to provide a weak index guide. Basically,oxide layer 18″ will provide a weak index confinement for the opticalmodes, providing greater stability with temperature of the opticalmodes, while proton implant layer 18 will provide the electrical currentconfinement.

Another alternative for a red light VCSEL device configuration and itsfabrication process is shown in the representative schematic diagram ofFIG. 13. In this case, an etch into capping layer 17 and mirror 13 ofFIG. 9 is performed, preferably one that leaves a slight positive slopein that resulting mirror, 13′ and in resulting capping layer, 17′, in amodified VCSEL, 10′″, in FIG. 13. The metal for a metal interconnection,19′, with an aperture is then deposited so that it covers this etchedsloping sidewall in providing this interconnection. The purpose of thisconfiguration is to further improve the heat removal from the devicebecause the heat generated therein during operation is conducted moreeffectively in the lateral direction than in the vertical direction inthe structure. This arrangement allows the metal to be in contact withthe sidewalls and several layers in the structure to more easily removeheat from the device. The ability to use AlAs, which has a higherthermal conductivity than the AlGaAs alloy, in the mirrors which theproton implant design allows further facilitates this heat removal. Asmentioned above, this option is allowed by the use of protonimplantation for the gain guide, but is not available to use if the gainguide is an oxide aperture. Furthermore, the arrangement also allows theisolation implant to penetrate deeper into the device, or alternatively,allows for a lower energy implant.

Another arrangement, 10 ^(iv), for the electrical contact structure of ared light emission VCSEL is shown in FIG. 14. In this arrangement, metalcontacts, 26, suited for ohmic connection to n-type conductivitymaterial make electrical contact to a surface provided parallel to thesubstrate of a modified n-type conductivity cladding layer 15′ in activeregion 14 at n-type conductivity mirror, 12. Further, metal contacts,27, suited for ohmic connection to p-type conductivity material makeelectrical contact to a surface provided parallel to the substrate of amodified p-type conductivity mirror, 13′. Thus, contacts to the pnjunction of the VCSEL device are made to a cladding layer and a mirrorlayer in and near active region 14 within VCSEL device 10′″ rather thanbeing formed to the substrate and emission surface of the device. Thisarrangement requires etching two mesas—one mesa is etched in the portionof p-type conductivity mirror 13 of FIG. 9 near to active region 14 toform modified mirror 13′ of FIG. 14 (or alternatively the top of p-typecladding region 16 in active region 14 suitably modified) for contacts27, while the other mesa is etched in the portion of n-type conductivitycladding layer 15 of FIG. 9 in active region 14 to form modifiedcladding layer 15′ of FIG. 14 (or the portion of the n-type conductivitymirror 12 near active region 14 suitably modified) for contacts 26. Theimplementation of this approach can be facilitated by using thickercladding layers (but designed so that the overall cavity has an opticalthickness which is an integer number of the emission wavelength), orseparate contact layers within the mirrors. Etch stop layers (typicallythin layers which are not etched by the same wet or dry chemistry usedto etch the rest of the structure) can be used to stop precisely at thedesired layer.

This arrangement places the metal interconnection layers, whichtypically have a high thermal conductivity, as close to the activeregion as possible to enable the removal of heat generated during deviceoperation. Furthermore, current does not have to be passed through thehigher resistance mirror layers thereby minimizing the heat generationduring operation due to electrical resistance.

FIG. 15 shows a representative schematic diagram of a VCSEL arrayarrangement to maintain a constant thermal load on VCSEL devices tominimize the thermally induced time dependence of their performances.For instance, the output of one VCSEL may decrease, or even increase, asthe result of a neighboring device being switched on to emit red lighton. The structure of FIG. 14 pairs a VCSEL device 10, as an example,which emits light, with a second device, 10 ^(v), which is identicalexcept that there is no opening in the metal to allow light emission. Inuse, current would be switched between the light emitting device and theclosed device during operation. When one wishes to turn off one of VCSELdevices 10, one switches the current to its closed aperture counterpart.The thermal load on the chip should remain nearly the same. While thefigure shows two rows of devices: one row with normal apertures, and theother with closed apertures, a variety of other geometrical arrangementsare possible depending upon the intended uses therefor.

Other ways for managing the thermal heat generation and removal includethe use of an overcoating on the chip with a polymer or dielectric layerwith a high thermal conductivity, such as diamond, or aluminum nitride(AlN). The use of solder to attach the die to the package, rather thanconductive epoxy may improve the heat removal through the package.Thinning the substrate to less than 100 μm and attaching the die to ahigh thermal conductivity submount may improve the heat removal.

Another arrangement for heat removal is shown in a representativeschematic diagram of a VCSEL array packaging configuration in FIG. 16.In this configuration the device bond pads, 28, are plated with thickmetal with red light VCSELs 10, for example, positioned between them,and the resulting array device is mounted by solder or stud bumping to atransparent superstrate, 29, preferably one with superior thermalconductance. The proximity of devices 10 to metal lines 28 carrying awaythe heat is advantageous for those devices.

Alternatively, GaAs substrate 11 could be removed after the device ismounted to superstrate 29, and contacts could be made to the back sideof the VCSEL devices. The chip or wafer would then be mounted on a highthermal conductivity submount, which now no longer needs to betransparent. This would also facilitate removal of the heat.

A further representative schematic diagram of a VCSEL array packagingconfiguration is shown in FIG. 17. In this package, following partialfabrication of the VCSEL structure (the formation of the proton implantor oxide aperture in a VCSEL 10 for example), the wafer with thepartially fabricated VCSELs can be attached at an exposed surface ofp-type conductivity mirrors 13 therein, for example, to a submountcoated with a thick, thermally conductive metal layer, 30. The originalGaAs substrate 11 is then removed, and a metal contact, 31, is depositedand patterned on the now exposed surface of the remaining structureoriginally located next to GaAs substrate 11 (n-type conductivity mirror12 in this example). This metal contains open apertures allowing thelight to escape from the center of each VCSEL. The result also allowsfor the use of a thick metal layer in close proximity to active region14 to facilitate heat removal from the device.

A representative schematic diagram of a VCSEL device packagingconfiguration with active heat removal is shown in FIG. 18. In thispackage, the VCSEL structure could be any of the configurations alreadydescribed, or some combination of those configurations. A VCSEL device10, as an example, is placed directly upon a thermo-electric cooler, 32,to control the temperature of the device during its operation.Thermoelectric coolers are standard microelectronic components forcontrolling the temperature of circuit or other heat generatingoperating devices, such as an optoelectronic device or an integratedcircuit, and can be purchased in sizes small enough to fit inside a TOheader style package, 33. Alternatively, a thermoelectric cooler couldbe monolithically integrated by first growing a number of GaAs pnjunctions for such a cooler on a GaAs substrate, before the growth andprocessing of the VCSEL structure materials to thereby form VCSELdevices. A stack of around 5 to 20 pn junctions would be grownsequentially one on top of the previous each on the order of 1,000 to5,000 Å thick as the basis for the cooler. The junctions can beelectrically interconnected in parallel through selective etching andmetallization interconnection, or electrically interconnected in seriesthrough use of intermediate tunnel junctions. Active cooling of VCSELdevices allows keeping them in suitable temperature ranges in which thedesired performances can be achieved.

In the devices set out in the foregoing, the key consideration for themirrors is to reduce the series electrical resistance thereof and theoptical absorption therein which in turn results in less heating of thedevice. This is accomplished by increasing the width of the gradedlayers in the mirror, reducing the doping levels in the mirror close tothe active region, and increasing the doping level in the mirrorrepeating material layer periods further away from the active region.Reduction of resistance, and therefore heating, is also addressed byheavily doping the layers of the p-type conductivity mirror farthestfrom the active region to reduce the contact and lateral resistance.

Within the active region, the choices available are made to minimize theimpact of heating. The choice of quantum wells with compressive strain,combined with either lattice matched or tensile strained barrier layers,improves the carrier confinement in the active region, thus increasingthe temperature range of operation. The use of a more highly p-dopedregion in the p-type spacer or cladding layer confines electrons to theactive region, and prevents them from being injected into the p-typeconductivity mirror. Layer composition choices and grading is also donewith the objective of improving carrier confinement.

Thermal conductivity must also be improved so that heat can be removedmore effectively from the device. The use of the proton implantedstructures combined with AlAs containing mirror contributes to thatobjective. The width of the isolation implant region is limited with theobjective of improving thermal conductivity. Etching of the top mirror,and deposition of metal on the etched sidewalls provides a path for heatremoval. The deposition of a thermally conductive dielectric, the use ofsolder in the package, and the packaging structures described for moreeffectively providing a short thermal path from device to package areall designed to remove heat from the device more quickly andeffectively. In general, these enhancements will increase the outputpower, reduce the threshold current for lasing, reduce the resistance,and increase the temperature range over which the devices successfullyoperate.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

1. A laser system having a semiconductor material vertical cavitysurface emitting laser for emitting narrow linewidth light, said lasercomprising: a compound semiconductor material substrate; at least twofirst mirror pairs of semiconductor material layers in a first mirrorstructure on said substrate of a first conductivity type with each pairmember differing from that other in at least one constituentconcentration and separated from one another by a first mirror memberspacer layer with a graded constituent concentration, and each firstmirror pair separated from that one remaining by a first mirror pairspacer layer with a graded constituent concentration; an active regionon said first mirror structure with plural quantum well structurescomprising alternating layers of GaInP and AlGaInP with said quantumwell structures being separated from said first mirror structure by atleast one active region spacer layer; at least two second mirror pairsof semiconductor material layers in a second mirror structure on saidactive region of a second conductivity type with each pair memberdiffering from that other in at least one constituent concentration andseparated from one another by a second mirror member spacer layer with agraded constituent concentration, and each second mirror pair separatedfrom that one remaining by a second mirror pair spacer layer with agraded constituent concentration; a gain guide layer proton implantbased structure having a relatively greater electrical resistivity thansaid second mirror structure where located at least in part therein soas to surround an aperture region of said second mirror structure acrossfrom said active region and to be positioned separated from said activeregion by at least said two second mirror pairs of semiconductormaterial layers but less than six such second mirror pairs in saidsecond mirror structure, said aperture region having pairs of sideportions thereof each intersected by an axis common thereto that isparallel to said substrate and perpendicular to one other such axis witheach said side portions in each said pair separated from one another by6 μm to 12 μm; and a pair of electrical interconnections to said laserseparated from one another by said substrate, said first mirrorstructure, said active region and said second mirror structure.
 2. Thelaser system of claim 1 wherein said quantum well structures layers ofGaInP are under stress in one direction and said quantum well structureslayers of AlGaInP are under stress in an opposite direction.
 3. Thelaser system of claim 2 wherein said active region is separated fromsaid first mirror structure by a active region spacer layer having twoAlGaInP sublayers therein with that sublayer farthest from said firstmirror structure being graduated in aluminum and gallium concentrationsover a selected thickness.
 4. The laser system of claim 1 wherein saidfirst mirror member spacer layer and said first mirror pair spacer layereach have a thickness exceeding 15 nm.
 5. The laser system of claim 1further comprising a spreading layer on said second mirror structurehaving a thickness equaling an odd number of quarter wavelengths of saidnarrow linewidth light that said laser can emit.
 6. The laser system ofclaim 1 wherein said two first mirror pairs of semiconductor materiallayers each have one said semiconductor layer pair member therein formedof AlAs and that remaining one of said semiconductor layer pair membersformed therein of AlGaAs with said first mirror member spacer layer andan adjacent said first mirror pair spacer layer together having athickness equaling a half wavelength of said narrow linewidth light thatsaid laser can emit.
 7. The laser system of claim 6 wherein saidsemiconductor layer pair members of AlAs are each equal in opticalthickness to said semiconductor layer pair members of AlGaAs.
 8. Thelaser system of claim 6 wherein said semiconductor layer pair members ofAlAs are each optically thicker than said semiconductor layer pairmembers of AlGaAs.
 9. The laser system of claim 1 wherein said first andsecond mirror structures are of opposite conductivity types.
 10. Thelaser system of claim 1 wherein said first and second mirror structuresare both of n-type conductivity and said active region further comprisesa pn tunnel junction.
 11. The laser system of claim 1 wherein saidactive region further comprises a zinc doped layer of relatively largeconductivity separated from any GaInP layers therein by at least 27 nm.12. The laser system of claim 1 wherein said active region spacer layeris a first active region spacer layer of n-type conductivity AlGaInP andfurther comprising said active region being separated from said secondmirror structure by a second active region spacer layer of p-typeconductivity AlGaInP.
 13. The laser system of claim 1 wherein saidactive region spacer layer is a first active region spacer layer ofn-type conductivity AlAs and further comprising said active region beingseparated from said second mirror structure by a second active regionspacer layer of p-type conductivity AlAs.
 14. The laser system of claim1 further comprising an isolation enclosing shell region in said laserextending along and surrounding an axis perpendicular to said substrateand surrounding but spaced apart from said aperture region of saidsecond mirror structure in said gain guide layer structure.
 15. Thelaser system of claim 1 wherein that one of said pair of electricalinterconnections made to said laser that is closer to said second mirrorstructure has an aperture opening therein across from said apertureregion.
 16. The laser system of claim 15 further comprising atransparent mount and wherein that one of said pair of electricalinterconnections made to said laser that is closer to said second mirrorstructure is electrically interconnected to said mount.
 17. The lasersystem of claim 15 further comprising an electrically conductive mountand wherein that one of said pair of electrical interconnections made tosaid laser that is closer to said second mirror structure iselectrically interconnected to said mount, and wherein further saidsubstrate has a metal contact made thereto with an aperture openingtherein across said first mirror structure and said active region fromsaid aperture region.
 18. The laser system of claim 1 wherein said laseris a first laser and wherein that one of said pair of electricalinterconnections made to said first laser that is closer to said secondmirror structure thereof has an aperture opening therein across fromsaid aperture region therein, and further comprising a secondsemiconductor material vertical cavity surface emitting laser on saidsubstrate adjacent to said first laser that is similar to said firstlaser except for that one of said pair of electrical interconnectionsmade to said second laser that is closer to said second mirror structurethereof is without an aperture opening therein.
 19. The laser system ofclaim 18 further comprising an isolation enclosing shell region in saidfirst laser extending along and surrounding an axis perpendicular tosaid substrate and surrounding but spaced apart from said apertureregion of said second mirror structure in said gain guide layerstructure of said first laser and located in part between said firstlaser and said second laser.
 20. The laser of claim 1 wherein said gainguide layer structure is a first gain guide layer structure and saidaperture region of said second mirror structure is a first apertureregion, and further comprising a second gain guide layer structureformed of an oxide material to have a relatively greater electricalresistivity than said second mirror structure where located at least inpart therein and on a side of said first gain guide layer structureopposite that side thereof closer to said active region so as tosurround a second aperture region of said second mirror structure acrossfrom said first aperture region.
 21. The laser of claim 20 wherein thatone of said pair of electrical interconnections made to said laser thatis closer to said second mirror structure has an aperture openingtherein across from said second aperture region.
 22. The laser of claim1 wherein a surface of said first mirror structure parallel to saidsubstrate extends past said active region and has made thereto one saidpair of electrical interconnections made to said laser, and wherein asurface of said second mirror structure parallel to said substrate isacross from said gain guide layer structure without being across fromsaid aperture region and has made thereto that remaining one said pairof electrical interconnections made to said laser.
 23. The laser systemof claim 1 wherein said substrate has a thickness less than 100 μm andfurther comprising said substrate being bonded to a base having a largethermal conductivity.
 24. The laser system of claim 23 wherein said baseis electrically conductive and serves as one of said pair of electricalinterconnections made to said laser.
 25. A semiconductor materialvertical cavity surface emitting laser for emitting narrow linewidthlight, said laser comprising: a compound semiconductor materialsubstrate; at least two first mirror pairs of semiconductor materiallayers in a first mirror structure on said substrate of a firstconductivity type with each pair member differing from that other in atleast one constituent concentration and separated from one another by afirst mirror member spacer layer with a graded constituentconcentration, and each first mirror pair separated from that oneremaining by a first mirror pair spacer layer with a graded constituentconcentration; an active region on said first mirror structure withplural quantum well structures comprising alternating layers of GaInPand AlGaInP with said quantum well structures being separated from saidfirst mirror structure by at least one active region spacer layer, saidactive region further comprising a zinc doped layer of relatively largeconductivity separated from any GaInP layers therein by at least 27 nm;at least two second mirror pairs of semiconductor material layers in asecond mirror structure on said active region of a second conductivitytype with each pair member differing from that other in at least oneconstituent concentration and separated from one another by a secondmirror member spacer layer with a graded constituent concentration, andeach second mirror pair separated from that one remaining by a secondmirror pair spacer layer with a graded constituent concentration; a gainguide layer structure formed of an oxide material to have a relativelygreater electrical resistivity than said second mirror structure wherelocated at least in part therein so as to surround an aperture region ofsaid second mirror structure across from said active region and to bepositioned separated from said active region; and a pair of electricalinterconnections to said laser separated from one another by saidsubstrate, said first mirror structure, said active region and saidsecond mirror structure.
 26. The laser system of claim 25 wherein saidquantum well structures layers of GaInP are under stress in onedirection and said quantum well structures layers of AlGaInP are understress in an opposite direction.
 27. The laser system of claim 26wherein said active region is separated from said first mirror structureby a active region spacer layer having two AlGaInP sublayers thereinwith that sublayer farthest from said first mirror structure beinggraduated in aluminum and gallium concentrations over a selectedthickness.
 28. The laser system of claim 25 wherein said first mirrormember spacer layer and said first mirror pair spacer layer each have athickness exceeding 15 nm.
 29. The laser system of claim 25 furthercomprising a spreading layer on said second mirror structure having athickness equaling an odd number of quarter wavelengths of said narrowlinewidth light that said laser can emit.
 30. The laser system of claim25 wherein said first and second mirror structures are of oppositeconductivity types.
 31. The laser system of claim 25 wherein said firstand second mirror structures are both of n-type conductivity and saidactive region further comprises a pn tunnel junction.
 32. The lasersystem of claim 25 wherein said active region spacer layer is a firstactive region spacer layer of n-type conductivity AlGaInP and furthercomprising said active region being separated from said second mirrorstructure by a second active region spacer layer of p-type conductivityAlGaInP.
 33. The laser system of claim 25 wherein said active regionspacer layer is a first active region spacer layer of n-typeconductivity AlAs and further comprising said active region beingseparated from said second mirror structure by a second active regionspacer layer of p-type conductivity AlAs.
 34. The laser system of claim25 further comprising an isolation enclosing shell region in said laserextending along and surrounding an axis perpendicular to said substrateand surrounding but spaced apart from said aperture region of saidsecond mirror structure in said gain guide layer structure.
 35. Thelaser system of claim 25 wherein that one of said pair of electricalinterconnections made to said laser that is closer to said second mirrorstructure has an aperture opening therein across from said apertureregion.
 36. The laser system of claim 35 further comprising atransparent mount and wherein that one of said pair of electricalinterconnections made to said laser that is closer to said second mirrorstructure is electrically interconnected to said mount.
 37. The lasersystem of claim 35 further comprising an electrically conductive mountand wherein that one of said pair of electrical interconnections made tosaid laser that is closer to said second mirror structure iselectrically interconnected to said mount, and wherein further saidsubstrate has a metal contact made thereto with an aperture openingtherein across said first mirror structure and said active region fromsaid aperture region.
 38. The laser system of claim 25 wherein saidlaser is a first laser and wherein that one of said pair of electricalinterconnections made to said first laser that is closer to said secondmirror structure thereof has an aperture opening therein across fromsaid aperture region therein, and further comprising a secondsemiconductor material vertical cavity surface emitting laser on saidsubstrate adjacent to said first laser that is similar to said firstlaser except for that one of said pair of electrical interconnectionsmade to said second laser that is closer to said second mirror structurethereof is without an aperture opening therein.
 39. The laser system ofclaim 38 further comprising an isolation enclosing shell region in saidfirst laser extending along and surrounding an axis perpendicular tosaid substrate and surrounding but spaced apart from said apertureregion of said second mirror structure in said gain guide layerstructure of said first laser and located in part between said firstlaser and said second laser.
 40. The laser of claim 25 wherein a surfaceof said first mirror structure parallel to said substrate extends pastsaid active region and has made thereto one said pair of electricalinterconnections made to said laser, and wherein a surface of saidsecond mirror structure parallel to said substrate is across from saidgain guide layer structure without being across from said apertureregion and has made thereto that remaining one said pair of electricalinterconnections made to said laser.
 41. The laser system of claim 25wherein said substrate has a thickness less than 100 μm and furthercomprising said substrate being bonded to a base having a large thermalconductivity.
 42. The laser system of claim 41 wherein said base iselectrically conductive and serves as one of said pair of electricalinterconnections made to said laser.
 43. A semiconductor materialvertical cavity surface emitting laser for emitting narrow linewidthlight, said laser comprising: a compound semiconductor materialsubstrate; at least two first mirror pairs of semiconductor materiallayers in a first mirror structure on said substrate of a firstconductivity type with each pair member differing from that other in atleast one constituent concentration and separated from one another by afirst mirror member spacer layer with a graded constituentconcentration, and each first mirror pair separated from that oneremaining by a first mirror pair spacer layer with a graded constituentconcentration, said first mirror member spacer layer and said firstmirror pair spacer layer each having a thickness exceeding 15 nm; anactive region on said first mirror structure with plural quantum wellstructures comprising alternating layers of GaInP and AlGaInP with saidquantum well structures separated from said first mirror structure by atleast one active region spacer layer; at least two second mirror pairsof semiconductor material layers in a second mirror structure on saidactive region of a second conductivity type with each pair memberdiffering from that other in at least one constituent concentration andseparated from one another by a second mirror member spacer layer with agraded constituent concentration, and each second mirror pair separatedfrom that one remaining by a second mirror pair spacer layer with agraded constituent concentration, said second mirror member spacer layerand said second mirror pair spacer layer each having a thicknessexceeding 15 nm; a gain guide layer structure formed of an oxidematerial to have a relatively greater electrical resistivity than saidsecond mirror structure where located at least in part therein so as tosurround an aperture region of said second mirror structure across fromsaid active region and to be positioned separated from said activeregion; and a pair of electrical interconnections to said laserseparated from one another by said substrate, said first mirrorstructure, said active region and said second mirror structure.
 44. Thelaser system of claim 43 wherein said quantum well structures layers ofGaInP are under stress in one direction and said quantum well structureslayers of AlGaInP are under stress in an opposite direction.
 45. Thelaser system of claim 44 wherein said active region is separated fromsaid first mirror structure by a active region spacer layer having twoAlGaInP sub layers therein with that sublayer farthest from said firstmirror structure being graduated in aluminum and gallium concentrationsover a selected thickness.
 46. The laser system of claim 43 furthercomprising a spreading layer on said second mirror structure having athickness equaling an odd number of quarter wavelengths of said narrowlinewidth light that said laser can emit.
 47. The laser system of claim43 wherein said first and second mirror structures are of oppositeconductivity types.
 48. The laser system of claim 43 wherein said firstand second mirror structures are both of n-type conductivity and saidactive region further comprises a pn tunnel junction.
 49. The lasersystem of claim 43 wherein said active region spacer layer is a firstactive region spacer layer of n-type conductivity AlGaInP and furthercomprising said active region being separated from said second mirrorstructure by a second active region spacer layer of p-type conductivityAlGaInP.
 50. The laser system of claim 43 wherein said active regionspacer layer is a first active region spacer layer of n-typeconductivity AlAs and further comprising said active region beingseparated from said second mirror structure by a second active regionspacer layer of p-type conductivity AlAs.
 51. The laser system of claim43 further comprising an isolation enclosing shell region in said laserextending along and surrounding an axis perpendicular to said substrateand surrounding but spaced apart from said aperture region of saidsecond mirror structure in said gain guide layer structure.
 52. Thelaser system of claim 43 wherein that one of said pair of electricalinterconnections made to said laser that is closer to said second mirrorstructure has an aperture opening therein across from said apertureregion.
 53. The laser system of claim 52 further comprising atransparent mount and wherein that one of said pair of electricalinterconnections made to said laser that is closer to said second mirrorstructure is electrically interconnected to said mount.
 54. The lasersystem of claim 52 further comprising an electrically conductive mountand wherein that one of said pair of electrical interconnections made tosaid laser that is closer to said second mirror structure iselectrically interconnected to said mount, and wherein further saidsubstrate has a metal contact made thereto with an aperture openingtherein across said first mirror structure and said active region fromsaid aperture region.
 55. The laser system of claim 43 wherein saidlaser is a first laser and wherein that one of said pair of electricalinterconnections made to said first laser that is closer to said secondmirror structure thereof has an aperture opening therein across fromsaid aperture region therein, and further comprising a secondsemiconductor material vertical cavity surface emitting laser on saidsubstrate adjacent to said first laser that is similar to said firstlaser except for that one of said pair of electrical interconnectionsmade to said second laser that is closer to said second mirror structurethereof is without an aperture opening therein.
 56. The laser system ofclaim 55 further comprising an isolation enclosing shell region in saidfirst laser extending along and surrounding an axis perpendicular tosaid substrate and surrounding but spaced apart from said apertureregion of said second mirror structure in said gain guide layerstructure of said first laser and located in part between said firstlaser and said second laser.
 57. The laser of claim 43 wherein a surfaceof said first mirror structure parallel to said substrate extends pastsaid active region and has made thereto one said pair of electricalinterconnections made to said laser, and wherein a surface of saidsecond mirror structure parallel to said substrate is across from saidgain guide layer structure without being across from said apertureregion and has made thereto that remaining one said pair of electricalinterconnections made to said laser.
 58. The laser system of claim 43wherein said substrate has a thickness less than 100 μm and furthercomprising said substrate being bonded to a base having a large thermalconductivity.
 59. The laser system of claim 58 wherein said base iselectrically conductive and serves as one of said pair of electricalinterconnections made to said laser.